Sheet handling apparatuses such as mail item handling machines that handle mail items such as postcards and letters include, for example, a loading unit, a recognition device (OCR), a stacking device, a rejection stacking device, a switchback device, a conveyance path connecting the devices, gates that distribute conveyed sheets to the respective devices, and so on. A plurality of sheets set in a supply unit of the loading unit are separated and taken out one by one by the loading unit, and conveyed to the recognition device. The recognition device recognizes the sheet, and determines a destination of the sheet (for example, the stacking device or the stacking device) and a conveyance route (for example, whether to cause the sheet to pass through the switchback device so as to be turned over). After that, the sheet is conveyed to the determined device via the conveyance path and a gate mechanism, and various types of processing are performed in that apparatus.
As the loading unit of such a sheet handling apparatus, a type of loading unit that takes out sheets by suction using a negative pressure has been proposed. This loading unit includes an air suction structure that picks up a sheet by suction using a perforated belt and an air chamber, and a separation roller that picks up a second sheet by suction and separates the second sheet from the first sheet so as to prevent the feeding of two sheets at once. The loading unit also includes an optical sensor for detecting whether there is a sheet in the supply unit that supplies sheets or whether the number of sheets in the supply unit is few or many. If the sensor determines that there is no sheet, the supply unit is operated to deliver the next sheet to a feeding position.
Using the sheet loading unit described above, in the case where the sheet has a low light reflectivity (for example, the sheet is black), the optical sensor cannot detect light reflected from the sheet, and thus it is difficult to accurately detect the presence of the sheet. Accordingly, the supply unit pushes the sheet at a speed that is higher than the ideal speed, and the sheets tend to jam in the feeding position. In this case, it may not be possible to feed the front most sheet in a stable manner, or there may be skewing or overlapped feeding of the sheets.
There is a need in the field for a sheet loading unit that can suppress anomalies in the sheet supply operation and feed sheets in a stable manner, and a sheet handling apparatus including such a sheet loading unit. Further, there is a need for a sheet loading unit that can detect sheets that have low light reflectivities.